their overly large size: the Bolo Mark I is described as weighing 150 tons, the Mark II 300 tons while the much more advanced Mark XXXIII, considered a standard model in the series, weighs 32,000 tonnes. These enormous tanks are also described as tank-carriers themselves.

their increasingly complex AI: Where first models are controlled by a programming intended to reduce the need for a human crew, later models mimic human thought patterns, feature strong AIs and finally Psychotronic circuitry, enabling self-awareness, strategic planning and decision-making, and even conscience.

minimized human crew, often consisting only of a single human commander who can either directly control all aspects of his unit thanks to an advanced interface, or who communicates with his unit, giving it instructions to carry out.

From the Mark III onwards, the standard Bolo design was intended to provide a consolidated set of capabilities intended to address virtually any combat situation, from operating underwater to engaging enemy units in land, sea, air and even space—the Mark XV/R was able to engage starships in low to medium orbit. Depending on the era and enemy capabilities, a single Bolo was often considered the equivalent of a manned armoured assault brigade or even a full army corps. While each Mark generally opted for a "balanced" approach to offensive and defensive capabilities, there were often specialised variations on the base model, such as heavy siege units, scout units and ECM platforms.

Prior to the Mark XIV, early Bolo Marks utilised projectile weapons for their main battery: a tank gun firing discarding sabot fin-stabilized long rod penetrator shells or a railgun. As the energy-storage capabilities of successive Bolo designs grew, these projectile weapons were replaced, initially by laser cannons, though these were quickly succeeded by the Hellbore: a plasma cannon derived from a battlecruiser's main battery.

Hellbore ammunition consists of slivers of highly pressurized frozen deuterium which, when fired, are ignited (by a laser) in a fusion reaction. The resulting bolt is contained and directed using strong magnetic fields in the breech and barrel. The resulting plasma travels at a considerable fraction of light speed and is not affected by planetary gravity. However, since the Hellbore was designed as naval armament for Concordiat warships, modifications had to be made to avoid losing a significant portion of the shot's energy to atmospheric attenuation. To this end, a fraction of a second prior to deuterium detonation, a laser is fired along the path of the bolt to create a momentary vacuum. Later Bolo marks are capable of internally manufacturing Hellbore rounds, using water as a raw material, whereby the deuterium isotope of hydrogen is separated and cooled cryogenically into splinters of frozen hydrogen.

The Hellbore first saw service with the Mark XIV and is generally mounted on a turret to provide maximum targeting capabilities. Some Marks experimented with the use of two lighter Hellbores in place of a single, larger cannon; later, heavier Marks generally mount several smaller "support" Hellbores in addition to the main battery. Hellbore power output is measured in megatons per second; the diameter of the tube is a more common quantifying measure. The Mark XIV mounted a single 25 cm Hellbore; the Mark XXXIII featured three 200 cm and sixteen 30 cm Hellbores. The Mark XXXIV carries a variant of the Hellbore known as the Hellrail, an anti-starship railgun weapon, possessing an output of 90 megatons per shot. Hellrails are designed for planetary defense and cannot normally be depressed to strike ground targets.

All Marks of Bolos are equipped with a set of secondary batteries, generally known as infinite repeaters. Depending on the era and Mark, this term covers the use of Gatling guns, anti-personnel flechette launchers, small-bore railguns, energy weapons and even small-caliber Hellbores. Other secondary armaments include indirect weaponry such as rapid-fire mortars, heavy howitzers, and surface-to-surface/surface-to-air missiles. Bolos can be equipped with thermonuclear weaponry, though the use of these on inhabited planets is generally restricted.

Mark XXXIIIs are known to carry Dragon hover-tanks and Wyvern flyers in combat to provide additional offensive and scouting capabilities. Many Marks also carry maintenance drones which can be deployed externally if required.

The armor of a Bolo Unit is designed to withstand direct hits from all weapons, including in some of the stories nuclear weapons. The armor types are named in the books as "durachrome", more advanced Bolos have "flintsteel",[2] then "duralloy" and "endurachrome". Many models would also use ablative or ceramic tiles to provide additional protection against plasma weapons.

All later Marks also had reactive armour designed to destroy incoming penetrator missiles that could bore through their regular armour. Beginning with the Mark XIX, Bolos also began to be protected by external energized battlescreens. These battlescreens could convert a significant percentage of enemy weapon fire into energy which could then be redirected to the Bolo's own systems and weapons. Also, beginning with the Mark XXIII, internal disruptor fields were added to limit damage to vital systems from any attacks which did manage to penetrate the Bolo's outer defenses.

Each unit is also equipped with passive and active sensors, as well as stealth and ECW capabilities. Later Marks were often also equipped with FTL comm. Bolos can also be equipped with stealthed reconnaissance drones and similar remote-sensing capabilities; several Marks even have the ability to utilise MILSAT spy satellites. Later Bolos also contain their own maintenance robots to repair battle damage.

Power for weapons, battlescreens, and mobility is most often provided by one or more fission or fusion energy sources, in conjunction with high-capacity batteries which are used as secondary or emergency power supplies. A Bolo's command center can remain operational for decades or centuries after reactor fuel is exhausted. As a last resort, Bolos may detonate their reactors to destroy an enemy, or prevent their capture.

Early Bolo models are not self-aware artificial intelligences and up through the Mark IX are only systems which automate the functioning of the vehicle under direct human command. Beginning with the Mark X, Bolos begin to use limited AI systems using pre-packaged battle plans which allowes them to function relatively independently provided the situation on the battlefield falls within the parameters of its pre-loaded plan. If not, the human commander needs to directly intervene either selecting a new battle plan or taking over the functions of the Bolo personally. This system is further advanced beginning with the Mark XV-R which is given a basic AI core capable of choosing between various pre-loaded plans based upon actual battlefield conditions. However, what these earlier Bolos are not capable of doing was developing their own independent battle plans.

Beginning with the Mark XX, Bolos are equipped with a psychotronic brain which gives them artificial intelligence. Analogous to human minds, psychotronic brains do turn insane when damaged. This occurs during battle or from neglect and lack of physical maintenance. Though not occuring frequently, the consequences are terrible due to a Bolo's enormous power. For this reason, early psychotronic brains (models XX through XXIII), restrict awareness and initiative at all times except during battle. This is accomplished by separating main processing from personality. The two are integrated (enabling the Bolo to come into possession of its full faculties) only when battle preconditions are met, such as the approach of an enemy or the order of a human officer. In later models, added redundancy reduces the likelihood of insanity and the restriction is relaxed to enhance intelligence. As a final safeguard, Bolos are equipped with a Total Systems Override Program (nicknamed Omega Worm) which erases the Bolo's software, rendering it brain-dead. This is triggered if a Bolo refuses an authorized order or if executed by a human operator.

The cognitive inhibitions are completely removed after a review of the combat performance, at the Battle of Santa Cruz (c. A.D. 3030), of experimental unit 23/B-0075-NKE (Nike). Nike's performance demonstrates the capabilities and reliability of fully autonomous psychotronics. Nike herself dies by Omega Worm as a result of refusing to obey an officer who is a traitor. This leads to a revision of the parameters for execution of Omega Worm in later model Bolos.

Beginning with the Mark XXV models, Bolos become completely autonomous, capable of full self-direction in all situations. However, it is found that the intuitive capabilities of human commanders working in conjunction with intelligent Bolos increases the effectiveness of the units and so, with some exceptions, human commanders continue to be assigned to, fight with and if necessary, die with their Bolos. This partnership is further enhanced with the introduction of the Mark XXXII which pioneers a neural interface which allows the Bolo and its human commander to mentally merge human intuition and Bolo processing speed.

Most later mark Bolos have several processing centers, the main core, the personality center, the damage control core (in later models) and the units survival center. Some Bolos were given a secondary main core however this was not typical. Of these the survival center is the most heavily protected, being at the center of the Bolo's mass directly under the human commander's command deck. In the event of the destruction of the Bolo the survival center is designed to protect the Bolo's core personality and programming for later retrieval and reactivation.

Each Bolo contains several computer "cores" with different functions, each of which contains multiple fully functional duplicates in case of failure. If a Bolo's logic becomes dysfunctional enough, it regresses to the original Resartus protocol, which is embedded in all self-aware models just for such a case.

A key factor in Bolo psychotronic design is the need to address public and military concern over the potential catastrophe which could be unleashed in the event of a Bolo disobeying orders or being suborned. To mitigate this, a number of safeguards are included in the psychotronic design—specifically a focus on loyalty, honour and a strong sense of duty, as well as a restriction on the level of awareness and processing power made available to the Bolo outside of combat. These safeguards often combine with the prejudices of ranking officers to cause the unnecessary destruction of a Bolo during combat.[3] With Bolos being able to survive for centuries, older Marks often end up scattered across the galaxy abandoned on old warfields or retrofitted for use in farming or heavy construction. On several occasions obsolete Bolos go rogue, causing significant destruction, loss of life and bad publicity for the Dinochrome Brigade: as a result, a special unit was set up to find all such units and burn out their control centers.

On several occasions, Bolos have turned against their commanders during combat: in Bolo!, a damaged Mark XXV loses its IFF capability, causing it to attack a fellow Bolo. Similarly, a Mark XXXIII (HCT/Hector) was subverted by an alien AI and turned into a prison guard in Bolo Strike. Conversely, Bolos have occasionally refused to carry out illegal or dishonourable orders, such as Unit NKE (Nike) in The Triumphant or Unit SOL (Surplus On Loan) in The Road to Damascus.

Bolos and their human commanders are assigned to an elite Concordiat unit called the Dinochrome Brigade, which traces its lineage back to various units on Earth. Individual Bolos are generally identified by a three-letter prefix which is generally extrapolated into a given name—this name is generally used as the default access code for a new commander. Often, Bolos on garrison duty are described as older surplus or reserve units on loan, in which case their three-letter prefix is changed to "SOL". [4]

Bolos are generally deployed in groups to provide fire support, though individual units are occasionally detached to perform garrison duty—later marks of Bolo are considered to be so capable that a single unit can be assigned to guard an entire planet, even during periods when a human commander is not available. Nevertheless, a commander is provided whenever it is feasible to do so. When deployed by the Dinochrome Brigade for major combat operations, Bolos usually serve with so called Planetary Siege Regiments. Before the development of higher marks of Bolos, powerful enough to often allow a single Bolo to conduct major planetary operations without support, the Regiments are only called siege regiments.

The Mark I is essentially described as a 150 tonne conventional tank powered by diesel engines and equipped with various servos and mechanical devices to reduce crew requirements. It is developed around the year 2000 by the fictional Bolo Division of General Motors.[5]

Conversely, the 300-tonne Mark III incorporates limited AI routines allowing limited independent action and is powered by ionic batteries able to support combat-level activity for up to ten years and enabling operation even when fully submerged.

The level of AI support increases with each successive Mark, until the incorporation of Psychotronic circuitry in the Mark XX led to Bolos becoming self-aware and capable of fully independent operation. (However, there are indications that the Mark XV Bolos approach sentience closer than is thought by the designers.) The Mark XXVI is described as capable of true independent strategic planning, while the final standardised Bolo, the 32,000-tonne Mark XXXIII is described as fully self-willed and able to operate indefinitely without external support.

As humanity spreads beyond Earth, Bolos are used to protect first the Empire, and then the Concordiat of Man. For millennia, each successive mark of Bolo proves to be the lynchpin of humanity's ground-based defenses, especially in the numerous and protracted wars against various aliens, most notably the Deng and the Melconians in the 30th century. Bolos are also used in smaller scale raids, skirmishes and internal conflicts between warring human parties.

The Mark XXXIII Bolo is the last standardised Bolo built by the Concordiat prior to the Melconian destruction of Earth. Following the genocide of the Final War with the Melconians, the surviving Bolos are described as crucial in sheltering and protecting the few scattered remnants of humanity during the long slow process of rebuilding. A number of seed corn colonies survive the genocide policies carried out by both sides and go on to produce new models of Bolo: these are generally labelled as Mark XXXIV and even larger in size, design and capabilities.

A species of parasites that invaded a human planet after the Concordiat and the 'Last War'. They subverted a bunch of Mk. XXXII Bolos by implanting them with copies of human consciousness, and used them to fight the Mk. XXXIIIs that Humanity (no longer the Concordiat) sent to liberate the planet. Aetryx infantry are genetically engineered brutes and they have some fairly heavy gravtanks, but nothing on the scale of a Bolo.

Anceti

An alien enemy of the Concordiat with some advanced technology that allows them to use time as a weapon.

Axorc

An alien foe of the Concordiat known for operating large crawler tanks similar to large, mechanized and armored centipedes. Little is mentioned about the Axorc other than their choice of multi-legged armored vehicles and that the Concordiat decisively overcame the Axorc. The Axorc were mentioned in Bolo Brigade.

Deng

Dog-sized spider-like aliens. Were the principal enemy of the human Concordiat for centuries, and unlike some alien species, treaties could be used with them. Primary weapons were 'Yavac' type armored vehicles. Unlike later authors, Keith Laumer always portrayed the light Yavacs as multi-legged walkers, while the heavier units were tracked, like Bolos. (Later authors missed or ignored this.) Primary weapons were deep UV lasers, as well as assortments of other weapons. Generally inferior to contemporary Bolos, the Deng required superior numbers to overcome Concordiat Bolos. Deng military organization operated large formations, and used numerous infantry forces.

Grakaan

An insectoid species with a vaguely humanoid appearance noted for a strong empire and a curious sense of humor. Their large empire, located far from the Galactic Core, has been known to resist all incursions into its territory and has never quarreled with humans of the Concordiat.

Humans

Humans created and operated Bolo war machines that defended the Concordiat. Humans often allied with alien races, but rarely mixed with alien species outside of trade and war purposes. Almost no human colonies mixed with alien beings under shared living conditions while the Concordiat existed, although a few, rare exceptions did occur.

Kezdai

A saurian-like race, fractionalized by clans which formed the basis of their political system, whose leadership tended to be military. The Kezdai began a campaign of expansionary conquests against Concordiat worlds during the period of total war with the Melconians. However, the Kezdai vastly underestimated the actual size of the Concordiat. Their actual threat level is around the same level as the Malach, a minor annoyance. The Kezdai military was organized around wheeled and counter-gravity vehicles (tracks did not appear to be used at all), with infantry in 'light' armor (i.e. not 'power armor') and extensive use of orbital fire support.

Khalesh

Briefly mentioned in Bolo Rising as an ally of the Melconian empire.

K'Juur

Briefly mentioned in Bolo Rising as a foe fought by Bolos in the fratricidal Outreach War.

Malach

Six-limbed raptor-like race, evolved from pack hunters in metal-poor old regions of the galaxy. Driven to conquest from old hunter instincts that had never worked out of their genetics. Malach society was ideologically an extremely militant social Darwinist group. The primary Malach ground weapon was a single-manned 'walker-type' capable of limited flight, atmospheric re-entry with a pod, and was armed with a variety of high energy weapons, magnetic shielding and low-yield tactical nuclear missiles. The Malach also employed unarmored infantry. The Malach operated a fleet based on large capital ship naval groups. The Malach were overall a small threat and their invasion was repulsed by a pair of old Mk. XXIV Bolos. If the regular Concordiat military had been deployed, the Malach most likely could have been easily crushed. (In Bolo Brigade, the Malach are mentioned, implying that most likely the Mk. XXX was the front-line Bolo. Given that two Mk. XXIVs were able to repulse the invasion, an actual Concordiat brigade and Navy force would have been able to crush them in short order.)

Melconian

Roughly human-sized anthropomorphic canids (bipedal dog-like humanoids), who were psychologically very similar to the humans of the Concordiat. The Melconians controlled a very large empire, with a long military history, estimated to be around twice the size of the Concordiat at its height. While they used heavy armor and infantry units in large numbers, Melconian infantry did not use heavy 'power armor' like the Concordiat. Unlike Bolos, which were designed to operate as single, independent combatants, Melconian heavy mechanized units were focused on a single battlefield role. Melconian technology was less advanced than the Concordiat's, and had no artificial intelligence in any of their mechanized units.

Quern

Major threat during the time where the Mk. XXIII was the front-line Bolo unit. Caused considerable damage during their invasion, striking into core worlds. Concordiat counter-attack resulted in what was believed to be the total annihilation of the Quern race and they were never heard from again.

Tersae

A primitive, vaguely anthropomorphic avian race (bipedal bird-like humanoids). The Tersae were a biologically-engineered species created by the Melconians in order to better understand sentience. The Melconians controlled the Tersae (who were divided into tribes) via a series of radios which beamed instructions to them. The Tersae came into conflict with humans at the orders of the Melconians, who were at the time altering them still further with increased aggression in mind. When humanity discovered the truth, the Melconians fled the system and released a Tersae-specific nerve gas, wiping out most of the population, but some survived with the help of the humans. The Melconians were not blamed at the time, as Earth and Melcon had not yet made first contact with each other. (Note: Not to be confused with the similar 'Tersae' of the BattleTech series, though ~very~ similar.)

Tolun

The Tolun (bipedal frog-like humanoids) are mentioned in Bolo Rising. The Tolun are sharp traders and always desire to learn new technologies even though their own is estimated to be considerably more advanced than present human technologies.

Vovoin

Briefly mentioned in Bolo Rising as a foe fought by Bolos in the fratricidal Outreach War.

Xalontese

Also known as Harpies. The Harpies invaded the Concordiat shortly after the introduction of the Mk. XXVIII Bolo to front-line service. The Harpy military utilized mass swarms of semi-sentient, flying suicide infantry (which resemble harpies, hence the nickname), supported by heavy close air support in the form of airship-like egg-shaped flying units. Ships were relatively slow, and their heaviest weapons could only fire straight down. However, the Harpy airships were massively armored and could resist the 110-cm Hellbores of the Mk. XXVIIIs for a considerable time. Briefly mentioned in Bolo Rising as a foe fought by Bolos in the Fringe Worlds War. Harpies also appear in the short story Shared Experience.

Yezhoth

In Bolo Rising, an old vessel of the Yezhoth is prepared by the !*!*! to transport humans and thus they are (or were) at least geometrically similar to humans.

!*!*!

The !*!*! are the chief antagonist in Bolo Rising and are a machine intelligence/civilization capable of subverting Bolos under the right conditions. They are believed to have originated somewhere in the galactic core and then rapidly expanded, destroying or conquering the organic civilizations they encountered. Their motivations are not well understood, but their martial technology is. The !*!*! employ Berzerker-like war machines of every size between an insect and a planetoid and have no compunction against flinging asteroids or rocks against planets with immense momentum, causing near nuclear-like devastation.

The specifics of their culture (assuming they even have one) are a mystery.

The story of the books takes place in various times from the near-future (2018, 2068), the mid-range future (27th up to 37th century) and even farther in one case (118th century). The overall plot features mostly military SF and includes space exploration, alien races and some advances in human society.

Many Bolo stories are told from the point of the view of the Bolo itself, with its internal thoughts printed in italics throughout the text.

One theme in Bolo works is the portrayal of valiant, tragic, self-sacrificing heroes, such as Bolo "Nike" in the story "Miles to Go" (Weber 1995, in Bolos Book III). Another concept explored by stories such as "Miles to Go" is the use (and abuse) of safeguards to prevent artificial intelligence from hurting its creators.[citation needed]

Their overall programming involves large amounts of human military history, and often they draw conclusions from that information which puts them at odds with their commanders. Sometimes Bolos develop senses of honor and nobility that would bring their actions into conflict with orders given by their human superiors. One of the stories in Rogue Bolo chronicles the actions of Combat Unit CSR, who identifies an alien threat to humanity but is forced to go "rogue" in order to defeat it (possibly for dramatic effect, as it does not appear to be explained why the bolo did not simply inform its commanders of the threat).